A. Field of the Invention
The present invention relates generally to exhaust systems utilized with motor vehicles. In particular, the present invention relates to vehicle exhaust recovery systems that cool and then recirculate a portion of the exhaust gases back to the engine to improve engine performance. Even more particularly, the present invention relates to exhaust systems that substantially remove particulate matter from the exhaust discharged by the vehicle to reduce pollution.
B. Background
Internal combustion engines have been and continue to be used in virtually every available mode of transportation and for all types of power supply needs throughout the entire world. Generally, internal combustion engines have a piston that is slidably disposed inside a cylinder with an explosive driving force being utilized to drive the piston in one or both directions in order to rotate an output shaft, such as a crankshaft, connected to the piston. The typical internal combustion engine comprises a plurality of cylinders that each have a piston reciprocating inside to drive a crankshaft in order to produce motion or power. Air and fuel are combined in the combustion chamber, defined inside the cylinder by the cylinder walls and the top of the piston, and then ignited by a spark from a spark plug or other sparking device (gasoline engines) or the heat of compression (diesel engines) to provide the explosive force that drives the piston downward. Air and fuel are fed into the combustion chamber through an air intake device and, after combustion, exhaust gases are forced out through an exhaust valve to a vehicle exhaust system that discharges the exhaust gases to the atmosphere. The typical vehicle exhaust system comprises a muffler configured to reduce the sound of the vehicle exhaust. Many vehicles also utilize, as often required by applicable laws and regulations, a catalytic converter to reduce the pollution associated with the vehicle exhaust.
Although the most common use for an internal combustion engine is to power a motor vehicle, such engines are also commonly utilized to generate electrical power and to power various other machines. For purposes of the present disclosure the term “internal combustion engine” is intended to include all such uses. The terms “motor vehicle” or “vehicle” include all motorized mobile devices that are powered by an internal combustion engine, including but not limited to cars, trucks, vans, motorcycles, scooters and all terrain vehicles (or ATVs). Over the years, the internal combustion engine has been the subject of intensive efforts in the United States and most industrialized countries to improve the operating characteristics of such engines. Despite these efforts, internal combustion engines are well known for relatively inefficient utilization of fuel, such as gasoline, diesel and other products primarily made from oil, and being significant contributors to the air pollution problems that exist in most cities and towns throughout the world.
One common desire for motor vehicle performance is that the vehicle achieve the best available power output (horsepower) and fuel efficiency (such as miles per gallon) for the least amount of fuel use. For instance, despite the availability of lower fuel consumption motor vehicles and vehicles which produce much less pollution, many people are reluctant to give up the size and power that is commonly associated with lower fuel efficiency and/or more polluting vehicles. In some circumstances, many people need higher horsepower output engines to more effectively power their heavy work vehicles, tow another vehicle and/or to drive in the hills or mountains.
Higher oil prices have resulted in higher fuel costs, particularly diesel and gasoline costs, in the United States and generally throughout the world and have highlighted the limited nature of this resource and the risks of a country being dependent on other countries for such an important commodity. Because of the desire to conserve a limited natural resource, reduce dependency on imported oil and spend less money on gasoline or other fuel, most people have a strong desire to improve the fuel efficiency of their motor vehicle. In addition, because of the problems plaguing most industrialized nations with regard to air pollution from motor vehicles, as well as other sources, there is also a strong desire to reduce hydrocarbon emissions from motor vehicles. As a result, there has generally been an increase in technology directed toward improving the fuel efficiency and reducing pollution emissions of motor vehicles while maintaining sufficient power output to achieve the desired use of the motor vehicle.
One known method of improving the performance of a motor vehicle, including fuel efficiency, emissions reduction and horsepower output, is to more throughly mix the air and fuel in the combustion chamber. More complete mixing of the air and fuel is known to provide more complete combustion, which results in more complete use of the vaporized fuel to increase fuel efficiency and power output and lower hydrocarbon emissions from an internal combustion engine. A typical internal combustion engine in a motor vehicle utilizes an air intake device, such as an air filter or air box, that feeds air to an air/fuel mixing device, such as a throttle body injector or carburetor, through an air duct or tube. It is generally well known that improved mixing of the air and fuel in the combustion chamber can be achieved by swirling the air flow prior to the addition of fuel in the air/fuel mixing device and by utilizing cooler intake air. Most air swirling devices, such as turbo charges and blowers, are installed upstream of the engine air intake device and are somewhat expensive and complicated devices that typically require ongoing maintenance. Other commercially available air swirling devices are configured to be installed inside an air intake device. Generally, however, these air swirling devices are sized and configured to be utilized with a specific carburetor or fuel injection system or to fit within a specific air intake device.
One type of system that has been developed to minimize the amount of pollutants, including nitrogen oxide (NOX) and like gases, that are discharged from internal combustion engines is an exhaust gas recirculation system. The typical exhaust gas recirculation system redirects a portion of the exhaust gas from the engine back into the air intake device where the exhaust gas is utilized as part of the engine's air intake supply. This recycling of the exhaust gas back into the combustion cycle lowers the air temperature thereof, which slows the combustion process and reduces the formation of nitrous oxides. In addition, the recycling of the exhaust gas allows the engine to burn any previously unburned hydrocarbons which would have been discharged to the atmosphere, thereby reducing pollution from the engine.
Cooling the exhaust gas prior to its recirculation into the air intake device is known to improve engine performance and reduce pollution associated with the vehicle emissions. Various cooling mechanisms, including air-to-air coolers, water coolers and other heat transfer devices, have been utilized to cool the exhaust gases being recycled to the engine by an exhaust gas recirculation system. In general, these systems have not been commercially successful due to the need for increased heat handling capability by the engine, such as larger radiators and the like. It is also known to use a vortex tube, also commonly referred to as a Ranque-Hilsch vortex tube, to separate a single exhaust gas stream into hot and cold (or at least cool) streams through differences in density. As known in the art, pressurized gas is received into a chamber defined by the tube that is configured to swirl the gas in a manner that directs the hotter air to the outer portion of the chamber and the cooler air to the inner portion of the chamber.
Over the years, various exhaust systems and devices have been patented to improve the performance of an internal combustion engine. For instance, U.S. Pat. No. 7,198,036 to White describes the use of a vortex tube connected to the engine air intake and an air tank to provide compressed air to an air valve at the input of the vortex tube. The compressed air is injected circumferentially into the vortex tube at sonic speed to create a cyclonic spinning effect within the tube to separate the air flow into cold and hot flows. U.S. Pat. No. 7,331,422 to Wall describes a vortex muffler having a stationary fan disposed in the inner passage of the muffler that creates a vortex in the inner passage to improve air flow through the muffler and reduce the exhaust sound level. U.S. Pat. No. 6,588,545 to Lee describes a muffler for internal combustion engines that comprises a vortex diffusing member mounted in the muffler casing which is connected to the exhaust inlet pipe to reduce exhaust sound and improve engine performance by allowing the exhaust gas to better flow through the muffler. U.S. Pat. No. 6,415,888 to An, et al. describes a muffler having a helicoil member in each conduit through which refrigerant gas flows that is configured to create a vortex flow for the refrigerant gas to reduce noise associated with a refrigerant gas compressor and improve the efficient operation thereof.
While the foregoing patents and other prior art disclose devices and systems that generally provide, or at least are intended to provide, more complete utilization of the exhaust gas from an internal combustion engine so as to improve performance of the engine and reduce pollution associated therewith, they have certain limitations that have generally limited their commercial acceptance. What is needed, therefore, is an improved system that effectively recirculates exhaust gas from an internal combustion engine to improve the performance of the engine and reduce pollution therefrom. The preferred exhaust gas recirculation system should be configured to be utilized with a wide variety of different types of internal combustion engines and, in particular, be installed on motor vehicles that utilize such engines. Preferably, such an improved system should direct cooled exhaust gas into the air intake device of an internal combustion engine to achieve more complete combustion of the engine fuel and discharge cleaner exhaust gas to the atmosphere to reduce pollution from the engine. The preferred exhaust gas recirculation system should include an improved muffler that can be installed in the engine exhaust system to redirect cooled exhaust gas to the air intake device and discharge cleaner exhaust gas to the atmosphere.